Second thoughts about material with spots (6)
I believe the answer is:
places
'spots' is the definition.
('place' can be a synonym of 'spot')
'second thoughts about material' is the wordplay.
'second thoughts' becomes 'ps' (as in P.S. in a letter).
'about' means one lot of letters goes inside another.
'material' becomes 'lace' (lace is a kind of material).
'ps' enclosing 'lace' is 'PLACES'.
'with' is the link.
(Other definitions for places that I've seen before include "Locations" , "Sites" .)